Several weight measuring devices are known in the art for the sensing of weight applied to a drill string and particularly to the drill bit for logging while drilling operations. One family of these weight indicating devices utilizes strain gauges mounted on elements within the apparatus that are deformed as a function of the weight applied to the apparatus. These devices suffer from problems associated with the delicate nature of strain gauges and their operation in the rather harsh environment at the bottom of a drill string. These devices which utilize strain gauges are limited due to the physical sensitivity of strain gauges when operating in high temperature environments and other environments where shock and vibration are present. The strain gauges, while noted for their accuracy in determining deformation of materials, are also noted for their delicate nature and exacting requirements regarding installation and operation in order to achieve accurate and meaningful measurements and results. Heretofore such weight measuring devices utilizing strain gauges have been felt to be unsatisfactory because of their delicate nature as well as their subseptibility to error due to exterraneous resistances that may appear in their associated circuitry.
Another family of weight indicating devices utilize a captive fluid chamber within a well tool wherein the weight applied to the tool alters the pressure in the captive fluid chamber and the change in pressure is recorded by a pressure recording instrument contained within and carried by the drill string. Such a device can be utilized only for the recording of weight applied to a drill bit or at some location within a drill string because the recording instrument must be removed from the drill string to analyze the recorded data once the drill string has been removed from the well.